Role of corneal collagen cross-linking in pseudophakic bullous keratopathy: a clinicopathological study.

OBJECTIVE: To evaluate the clinical and histopathologic changes induced by collagen cross-linking (CXL) in pseudophakic bullous keratopathy (PBK).

DESIGN: Randomized, prospective, interventional study.

PARTICIPANTS: Twenty-four patients with PBK were included in the study.

METHODS: Twenty-four patients with PBK underwent CXL followed by keratoplasty at 1 or 3 months. Twelve patients underwent penetrating keratoplasty 1 month after CXL (group A) and the remaining 12 patients underwent penetrating keratoplasty 3 months after CXL (group B). The main outcome measures were assessed at 1 week and 1 month for all patients and at 3 months for 12 patients only. The corneal buttons underwent histopathologic and immunofluorescence evaluation.

MAIN OUTCOME MEASURES: Visual acuity, ocular discomfort (tearing, redness, pain), corneal haze, central corneal thickness, histopathologic evaluation, and immunofluorescent microscopy.

RESULTS: Mean visual acuity showed a significant improvement after CXL, from 1.925 ± 0.173 before surgery to 1.75±0.296 at 1 month after surgery (P = 0.010), but deteriorated to 1.81 ± 0.23 at 3 months. Symptomatic relief after CXL was at a maximum at 1 month, with a worsening trend at 3 months. Eighteen patients showed a reduction in corneal haze 1 month after CXL. The effect was maintained in 9 of 12 patients at 3 months. The mean central corneal thickness decreased significantly from 846.46 ± 88.741 to 781.0 ± 98.788 μm at 1 month (P<0.01) after CXL, but increased to 805.08±136.06 μm at 3 months. Immunofluorescence microscopy revealed anterior stromal compaction in 7 of 12 patients (58.3%) in group A and in 5 of 12 patients (41.6%) in group B. Staining of keratocyte nuclei with 4',6-diaminido-2-phenylindole dihydrochloride (Molecular Probes, Carlsband, CA) revealed a relative uniform distribution throughout the stroma.

CONCLUSIONS: Collagen cross-linking causes symptomatic relief and a decrease in central corneal thickness and anterior stromal compaction in PBK. However, the effect decreases with time and depends on disease severity.